Bulletin d’avalanche

Stevens Pass

Northwest Avalanche Center
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Danger d’avalanche

Wed
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 4 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Tuesday should be a warm, soggy, and dangerous day. Wet loose slides are expected to grow large with daytime warming and light rain. Slides could become more destructive if they step down to older, deeply buried crusts. 

Problèmes avalancheux

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    We're in the middle of a warming trend with the snow level continuing to creep up the mountainsides. Wet loose avalanches should continue to grow larger as the day warms up, influenced by light rain then sunshine later. Signs of wet loose avalanche activity are rollerballs, and fresh fan-shaped avalanches with chunky looking debris.

    Stay off of, and out from underneath very steep slopes. Be especially careful of going underneath larger steep slopes where slides could pack more of a punch and hit you from above. At upper elevations, wet slides could entrain lots of snow and become large avalanches. They could also pull out wider slab avalanches on deeper layers. Above 5,500ft, NW-NE aspects harbor weaker, faceted grains over a crust from early March. This layer could be down close to 3ft deep in some areas, and any avalanche that runs on it would be very large. Tuesday is a good day to let the warm temperatures do their thing and stay away from steeper slopes while the snowpack slowly adjusts.

    Example large wet loose avalanche

    Photo: ONP Rangers

Avalanche Discussion

Numerous avalanches occurred on Monday with new snow and warming temperatures. WSDOT reported good slab results with control on the west side of the pass. Some paths slid sympathetically and pulled out older snow to more deeply buried crust layers. Small loose wet avalanches were easy to trigger by mid-morning, and one large natural was observed from low elevation, N facing slopes in Mill Creek. Later in the day a natural wet loose cycle was reported by Stevens Pass Ski Patrol. Visibility has largely inhibited observations of the surrounding higher elevation terrain.

We've been tracking a layer of faceted grains just above a crust from early March. Observers in the Chiwaukum range consistently found the March 8th facets above 5,000ft and reported significant wind loading on Saturday. On Friday, forecasters on Jim Hill and in the White Pine drainage confirmed the presence of the 3/8 facets and test results that indicate they could produce slab avalanches. See images and videos below. The layer could produce surprising avalanches where it exists under drifted slabs and may get overloaded by new snow and warming on Tuesday. You can find the weak layer 2-3 feet below the surface on NW-NE aspects above 5,500ft.  Elsewhere in the Cascades, this layer has produced very large slab avalanches, and it may just be a matter of time in the Stevens Pass zone.

Régions couvertes